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The research is related to solving the problem of rational use of materials and to creation of resource-saving technologies for the protection of the environment from pollution by various pollutants. Sorption technologies are quite effective in sewage treatment, but most sorbents are quite expensive, and their regeneration raises the question of recycling of spent solutions. The cheap and availability of raw material base of biosorbents makes these technologies attractive for wastewater treatment. The research is aimed at investigation of ways to effective utilization of spent sorbents, which are obtained after water purification, in the production of building materials. The obtained results allow create a complex low-waste technology of water demineralization and purification from heavy metal ions.

In this study, the processes of electrochemical oxidation of ammonia in a two-chamber electrolyzer with anion exchange membrane MA-41 were investigated. An estimation of the efficiency of the process of oxidation of ammonia, depending on the chemical composition of the initial solution of anolyte and catholyte, current density and time of electrolysis was carried out. It was shown that the oxidation of ammonia in the anode chamber passes quickly and is accompanied by a significant decrease in pH due to the formation of nitrogen dioxide and nitrates. At the same time, the current output and the electrical conductivity of the dilute solutions was rather low. The effect of chlorides on the process of electrolysis was investigated. It was shown that the presence of chlorides in the anolyte catalyzes the processes of oxidation of ammonia. An increase in the concentration of chlorides in the anolyte increases output and reduces electricity consumption. The presence of chlorides in the catholyte does not accelerate oxidation. The presence of sulfates, both in the anolyte and in the catholyte, slows down the process of oxidation of ammonia as a result of the oxidation of sulfates to persulfates, which are quite passive to ammonium ions. At the same time, electricity consumption increases.

The issue of desalination is relevant for many countries of the world; the most promising technology for demineralization appears to be membrane technology. The stabilizing treatment of water before feeding it to the membrane filters involved the ion exchange softening of the solution based on the weakly acidic cation exchanger DOWEX MAC-3 in the H+ and Na+ forms. This makes it possible to improve the efficiency of baromembrane desalination and the service time of membranes. The nanofiltration membrane OPMN-P ensures the purification of low mineralized waters from sulfates (by 74–93 %) and hardness ions (67–90 %); at the same time, the membrane has low selectivity in terms of bicarbonate anions and does not retain chlorides. This avoids the accumulation of these in the concentrates at the nanofiltration purification of low mineralized waters. The inverse osmotic membrane Filmtec TW30-1812-50 shows selectivity for sulfates and hardness ions of over 99 %. The selectivity for chlorides is 83–94 % for low mineralized water, and 90–95 % for highly mineralized water. The concentrates contain hardness ions, sulfates, chlorides, and bicarbonate anions in significant concentrations. We have defined conditions for the effective softening of the formed concentrates at the comprehensive treatment by lime and aluminum coagulants. When desalinizing the concentrate of low- and highly mineralized waters, the sulfate concentration decreased to 2.55–6.53 mg-equiv./dm3 and 3.31–9.02 mg-equiv./dm3, respectively. At the same time, the concentration of hardness ions was 3.31–9.02 mg-equiv./dm3 and 4.20–10.65 mg-equiv./dm3. Creating comprehensive technologies for the purification of mineralized waters makes it possible to ensure the proper efficiency of water desalination and to utilize the waste formed with obtaining useful products. That could reduce anthropogenic pressure on the environment and solve the problem of freshwater shortage for people and industry, Проблема опреснения воды актуальна для многих стран мира. Наиболее перспективными для деминерализации можно считать мембранные технологии. Для стабилизационной обработки воды перед подачей на мембранные фильтры использовали ионообменное умягчение раствора на слабокислотном катионите DOWEX MAC-3 в H+ и Na+ форме. Это позволяет повысить эффективность баромембранного обессоливания и срок эксплуатации мембран. Нанофильтрационная мембрана ОПМН-П обеспечивает очистку низкоминерализированной воды от сульфатов (на 74–93 %) и ионов жесткости (на 67–90 %), имеет низкую селективность по гидрокарбонат-анионах и не задерживает при этом мембрана хлориды. Это позволяет избежать накопления данных анионов в концентратах при нанофильтрационной очистке низкоминерализированной воды. Обратноосмотическая мембрана Filmtec TW30-1812-50 имеет селективность по сульфатам и ионам жесткости более 99 %. Селективность по хлоридам составляет 83–94% для низкоминерализированных вод и 90–95 % для высокоминерализованных. Концентраты содержат ионы жесткости, сульфаты, хлориды и гидрокарбонат анионы в значительных концентрациях содержат. Определены условия эффективного умягчения образованных концентратов при комплексной обработке известью и алюминиевыми коагулянтами. При обессоливании концентрата низко- и высокоминерализованных вод концентрация сульфатов снизилась до 2,55–6,53 мг-экв/дм3 и 3,31–9,02 мг-экв/дм3 соответственно. При этом концентрация ионов жесткости составляла 3,31–9,02 мг-экв/дм3 и 4,20–10,65 мг-экв/дм3. Создание комплексных технологий очистки минерализованных вод позволяет обеспечить надлежащую эффективность опреснения воды и переработать образованные отходы с получением полезных продуктов. Это позволит уменьшить антропогенное давление на окружающую среду и решить проблему дефицита пресной воды для населения и промышленности, Проблема опріснення води актуальна для багатьох країн світу. Найбільш перспективними для демінералізації можна вважати мембранні технології. Для стабілізаційної обробки води перед подачею на мембранні фільтри використовували іонообмінне пом’якшення розчину на слабокислотному катіоніті DOWEX MAC-3 в H+ і Na+ формах. Це дозволяє підвищити ефективність баромембранного знесолення та термін експлуатації мембран. Нанофільтраційна мембрана ОПМН-П забезпечує очищення низькомінералізованих вод від сульфатів (на 74–93 %) та іонів жорсткості (67–90 %), при цьому мембрана має низьку селективність по гідрокарбонат-аніонах і не затримує хлориди. Це дозволяє уникнути накопичення даних аніонів в концентратах при нанофільтраційному очищенні низькомінералізованих вод. Зворотньоосмотична мембрана Filmtec TW30-1812-50 має селективність по сульфатам та іонам жорсткості понад 99 %. Селективність по хлоридам становить 83–94 % для низькомінералізованих вод та 90–95 % для високомінералізованих. Концентрати містять іони жорсткості, сульфати, хлориди та гідрокарбонат аніони в значних концентраціях. Визначено умови ефективного пом’якшення утворених концентратів при комплексній обробці вапном та алюмінієвими коагулянтами. При знесоленні концентрату низько- та високомінералізованих вод концентрація сульфатів знизилась до 2,55–6,53 мг-екв/дм3 та 3,31–9,02 мг-екв/дм3 відповідно. При цьому концентрація іонів жорсткості становила 3,31–9,02 мг-екв/дм3 і 4,20–10,65 мг-екв/дм3. Створення комплексних технологій очищення мінералізованих вод дозволяє забезпечити належну ефективність опріснення води та переробити утворені відходи з отриманням корисних продуктів. Це дозволить зменшити антропогенний тиск на навколишнє природне середовище та вирішити проблему дефіциту прісної води для населення та промисловості

Heavy metals penetrate water reservoirs as a result of natural and anthropogenic processes, thereby accumulating in soil, bottom sediment, sludge, and can further migrate into groundwater and surface water. The main sources of heavy metals penetration into natural waters are the insufficiently treated waste waters from many branches of industry. That renders relevance to the problem of removing heavy metals from wastewater in order to prevent excessive pollution of water reservoirs. Among existing methods of water purification from heavy metals’ ions at significant volumes of industrial wastewater, the electrochemical methods are rather promising. The advantage of this method is a possibility to recycle the used regeneration solutions with obtaining metals that are suitable for reuse. This paper reports results of research into the processes of electrochemical removal of heavy metals’ cations from diluted aqueous solutions in one­and two­chamber electrolyzers. When conducting the study in a two­chamber electrolyzer, the anode and cathode regions were separated by the anion­exchanging membrane MA­40. A dependence of the influence of hardness, solutions’ pH, anodic current density, and the duration of electrolysis on efficiency of the removal of heavy metals’ ions was investigated. It is shown that the ions of zinc, copper and lead are effectively removed from aqueous solutions using the electrolysis at a starting concentration of 10 mg/dm3. It was established that at the low concentrations of ions, the output for current, when reducing metals, reached (4–20)·10­4 % and changed little with concentration. It was determined that the efficiency of water purification from heavy metals’ ions using electrolysis increases with an increase in pH of the medium and with a decrease in the hardness of water. In the two­chamber electrolyzers, these factors exert almost no effect on purification efficiency. The paper shows the prospect of using electrolysis for the selective removal of heavy metals from tap, softened and natural water. A given purification method makes it possible to not only post­clean wastewater to the maximally permissible concentrations, but also enables the purification of water from natural water bodies to the quality of drinking water

We report results of investigating the processes of electrochemical oxidation of ammonium in a two-chamber electrolyzer depending on the composition of the original solutions ‒ anolyte and catholyte, current density, electrolysis duration. It is shown that the electrochemical oxidation of ammonia in aqueous solutions of ammonium sulfate proceeds at a rate of 14‒55 mg/(dm 3 ·hours) at a current density of 86.2‒172.4 A/m 2 and the starting concentrations of a given ion of 10‒120 mg/dm 3 . The rate of ammonium oxidation under these conditions increases with increasing starting concentrations of ammonium and with increasing current density. The output of oxidized ammonium for current and specific consumption of electricity for water purification from ammonium are defined based on ammonium concentrations and current density and increase with an increase in the concentration of a given ion and a decrease in current density. Ammonium oxidation rate increases by 1.66 times in solutions of ammonium sulfate ([NH 4 + ]=90 mg/dm 3 , j=172.4 A/m 3 ) in tap water, compared with distilled water. This is due to the presence of chlorides in tap water, which act as a catalyst during ammonium oxidation at the expense of the intermediate formation of active chlorine. Under these conditions, we observed complete oxidation of ammonia compared with solutions on distilled water where the residual ammonium concentrations reach 1‒3 mg/dm 3 . It is shown that the presence of chlorides in catholyte at a concentration of 30 mg/dm 3 almost does not accelerate the oxidation of ammonium. Our work demonstrated thatекек in all cases, during oxidation of ammonium, pH of solutions decreases to 6.1‒2.0, which is predetermined by the oxidation of ammonium to nitrates and the acidification of water by the formed nitric and sulphuric acids. Based on the reported results, it can be concluded that the electrochemical method is the most promising method for the extraction of ammonium ions from water. Its application makes it possible to achieve a 100 % water purification.